Suitability of pre-digested dairy effluent for mixotrophic cultivation of the hydrogen-producing microalgae Tetraselmis subcordiformis

ABSTRACT

The costs associated with microalgal biomass production can be reduced by leveraging alternative and cheap growth media. Digestate from fermentation reactors is a particularly interesting candidate for use in cultivating mixotrophic species. The aim of the present study was to assess whether pre-digested milk-industry effluent can be harnessed to grow Tetraselmis subcordiformis and produce hydrogen. The experimental series with 25% and 50% effluent in the growth medium performed the best, producing more than 2000 mg_VS biomass/dm³. The biogas produced in these variants contained over 60% hydrogen. Increasing the effluent in the medium to 75% led to significant deterioration of performance, both in terms of T. subcordiformis biomass growth and biohydrogen production. The highest efficiency of nitrogen and phosphorus removal, respectively 98.1 ± 1.9% and 97.1 ± 1.4%, was observed in the system to which 25% of sewage was introduced. Increasing the share of fermented wastewater directly reduced the efficiency of removing biogenic compounds. A very strong negative correlation was found between initial N-NH₄ in the growth medium and T. subcordiformis biomass production rates (R² = 0.9177).

GRAPHICAL ABSTRACT

KEYWORDS:

• Green algae
• biohydrogen
• photobioreactor
• dairy wastewater
• anaerobic treatment

Disclosure statement

No potential conflict of interest was reported by the author(s).

Availability of data and materials

Manuscript has no associated data. The data are deposited and are available upon request.

Authors‘ contributions

Conceptualization: Marcin Dębowski and Magda Dudek; Methodology: Marcin Dębowski, Magda Dudek, Anna Nowicka and Piera Quattrocelli; Formal analysis and investigation: Anna Nowicka and Marcin Zieliński; Writing – original draft preparation: Marcin Dębowski and Joanna Kazimierowicz; Writing – review and editing: All Authors; Funding acquisition: Marcin Dębowski and Marcin Zieliński; Resources: Magda Dudek, Anna Nowicka and Piera Quattrocelli; Supervision: Marcin Dębowski, Magda Dudek and Joanna Kazimierowicz.

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

The manuscript was supported by Project financially supported by Minister of Education and Science (Poland) in the range of the program entitled ‘Regional Initiative of Excellence’ for the years 2019–2022, project no. 010/RID/2018/19, amount of funding: 12,000,000 PLN, and the work WZ/WB-IIŚ/3/2022, funded by the Minister of Education and Science (Poland).